great to have you with us. this is one of those sleeper issues that a lot of people don't pay attention to. and i see from the fact that we put together that one in three teachers this ten plus days in 180 days cool year. that sounds like a big number. what is going on? >> it is a lot, and this goes back decades. and the districts make bargains with teachers that instead of giving them big raises they give them a lot of time off. gerri: well, do you think it does anything for students' performance? and me, was the impact of the end of the day? >> well, the real harm is on student performance. we know that when teachers are absent from their classroom and anyone who has ever been to school will be able to tell you that when you have a substitute teacher, very little learning takes place. gerri: i seem to remember that myself. apparently this cost schools 4 billion per year, and why hasn't this issue really made its way to the front of the classroom when it comes to things that we need to solve in education? why